CABLE JOINTING
WHAT IS CABLE JOINTING & WHY DOES IT EXIST
Restrictions imposed by manufacturing process,
transportation and site conditions necessitate production of power cables in
specified lengths, which after installation, are joined and terminated at
pre-determined locations. Joints and terminations are an integral part of the
cable system, and are required to perform all the functions expected of the
cable itself. The complexities of a jointing system increases with the voltage
grade of the cable, the higher the voltage the more stringent are the requirements
to be met.
USE & NEED OF CABLE JOINTS
- An integral part of cable system
- Maintains the continuity of the cable
- Used in the event of cable failure
- Used to tap into existing cable
TYPE OF JOINTS
- Straight Joints for identical cable
- Transition Joints for different insulation cable
- Branched Joint to tap into existing Joint
VOLTAGE LEVEL
- Insulation requirement will increase with voltage Level
- Stress Control requirement varies with Voltage Level
ENVIRONMENTAL PROTECTION
- Joint must prevent water ingress into cable joint
MECHANICAL PROTECTION
- Joint must have enough mechanical strength to protect it from external damage
- The joint should be able to withstand thermo-mechanical stresses under short-circuit conditions or thermal effects of normal and permissible fault currents
STRESS CONTROL
The most critical aspect of high voltage cable jointing is
control of the dielectric stress originating at the point of screen
termination. Without the application of stress control, discharges would occur,
adversely affecting the life of the joint and termination
CONCLUSION
- Cable Joints are the weakest link in the cable system
- Joints design must have high degree reliability
- Joint must be robust & durable
- Types of cables to be joined, cable joint body interface & voltage transient greatly influence the design
- Stress Control problem must be addressed for reliable and safe joint
